Apparatus for centrifugally forming fibers



APPARATUS FOR CENTRIFUGALLY FORMING FIBERS Filed Oct. 27, 1958 6Sheets-Sheet 1 FUEL GAS GAS Fuel. 30d

INVENTORS I DALE KL E157' HENRY J SNaw ATM/5.

Aug. 23, 1960 D. KLElsT ET AL APPARATUS FOR CENTRIFUGALLY FORMING FIBERs6 Sheets-Sheet 2 Filed Oct. 27, 1958 fill;

BALL* KLBIST,

Aug. 23, 1960 D. KLEIST ETAL APPARATUS FOR CENTRIFUGALLY FORMING FIBERSFiled Oct. 27, 1958 6 Sheets-Sheet 3 INVENTORS: 7727,? .KEIS'I.' ENR? JENUW.

BY Wg Aug. 23, 1960 D. KLElsT ETAL APPARATUS FOR CENTRIFUGALLY FORMINGFIBERs 6 Sheets-Sheet 4 Filed Oct. 27, 1958 Aug. 23, 1960 n. KLElsT ETALAPPARATUS FOR CENTRIFUGALLY FORMING FIBERS 6 Sheets-Sheet 5 Filed Oct.27, 1958 INVENTORS.- DALE K 1.57-

BYHEN I i t\ @am Arm/5.

ug. 23, 1960 D. KLElsT ET AL APPARATUS FOR CENTRIFUGALLY FORMING FIBERSFiled 00h27, 195e 6 Sheets-Sheet 6 INVENTORSI DALE [(1,515 T HENRY J..5A/0W BY 'u vQJ/wvg Ohio, assignors to Owens-Coming FiberglasCorporation, a corporation of Delaware Filed Oct. 27, 1958, Ser. No.769,870 15 Claims. (Cl. 18-2.5)

This invention relates to apparatus for centrifugally forming finefibers from fiberizable material, for eX- ample from heat softenablevitreous material, such as glass.

This is a continuation-in-part of our co-pending application Serial N'o.594,803, which was led lune 29, :1956, now abandoned, and which will bereferred to herein as our previous application.

Our previous application disclosed and claimed a method and an apparatusfor attenuating ne fibers from vitreous materials, i.e., fromiiberizable materials such as glass, wherein a supply of molten glass isfed to a rotary centrifuge at a temperature at least sufiiciently highfor its attenuation into tine fibers by the kinetic energy from a blastof gaseous medium such as steam, into which the fiberizable material isprojected in the form of streams issuing from the centrifuge, bycentrifugal force created by Ithe rotation of the centrifuge. Theinstant application is directed to apparatus which constitutes animproved embodiment of the apparatus disclosed and claimed in ourearlier application. Concurrently herewith we are also @ling a-napplication directed to an improved method based upon the method of ourearlier applica- -tion as developed for commercial production and Whichalso is based upon the teachings and disclosure of our earlierapplication.

The principal object of the instant invention is, therefore, to provideapparatus for the attenuation of very fine fibers of generally increasedlength from material of the class described wherein the material isprojected from a rotary centrifuge at a temperature sufficiently highfor attenuation into a high velocity blast of gaseous medium from anannular blower which surrounds the centrifuge and which has one or moreheaters for the control of the temperature of the glass but which do notadd heat to the glass after it iirst enters the centrifuge. Indeed,among the concepts underlying the instant invention is the control ofthe temperature of the glass by proper operatio-n of the heaters inorder to control its rate of heat loss so that its temperaturecontinuously decreases from the time the glass first enters thecentrifuge until it is -nally attenuated into fine fibers; the apparatusof the invention being so designed and organized as to establish andmaintain this close control of the temperature of the glass and thus itsmore effective attenuation into fine fibers of great length.

It is another object of the invention to provide improved apparatus forthe formation of fine fibers by centrifuging fiberizable material -intoa gaseous attenuating blast by the combination of heaters designed andassembled according to the invention for the control of the environmentinto which the material is projected centrifugally and in which it issubject to the kinetic energy of the attenuating blast; this improvementincluding means for controlling the ambient air or other gases which areinduced into the system by the eductor atet C) effect of the expandingattenuating blast of gaseous medium.

It is yet another object of this invention to provide improved apparatusfor the attenuation of fine fibers from heat softened iiberizablematerial wherein the control ofthe operation is enhanced by means forcontrolling the density of induced gases which enter the system and bymeans for controlling the manner and location of their entrance; thedensity being controllable by the presence of structural gas flowrestricting means for reducing the quantity of the entering gases and/orby the use of a particularly located heater for increasing thetemperature of the gases or, in the most improved process by doing bothso as to most effectively control the attenuation and to produce thenest and longest fibers.

It is yet another object of this invention toprovide improved apparatus4for the attenuation of extremely fine glass bers at high productionrates which fibers have eXtreme length as well as fine diameters so thatupon their compaction into a blanket like massthe mass has anextraordinarily high parting strength.

Other and more specific objects and advantages of the invention will be`better understood by reference to the specification which follows andto the drawings in which:

Fig. 1 is a fragmentary, vertical, sectional View of a portion of rotarycentrifuging apparatus embodying the invention;

Fig. 2 is a view similar to Figure 1, but showing a modification of theapparatus;

Fig. 3 is a view in elevation on a greatly reduced scale of a commercialfiber forming line including a plurality of apparatuses embodying animproved modification of the invention;

Fig. 4 is a transverse, vertical, sectional view taken along the line 44 of Figure 3 and shown on a slightly enlarged scale;

Fig. 5 is a fragmentary, vertical, sectional View of one of theapparatuses shown in Fig. 3, on an enlarged scale;

Fig. 6 is a fragmentary, detailed, vertical, sectional view of yaportion of the apparatus shown in Figure 5, and

Fig. 7 is a fragmentary, horizontal, sectional view taken generallyalong the line 7-7 of Figure 6.

Preliminarily to the description of the particular figures of thedrawings and an explanation of how the apparatus shown therein isoperated, the operation carried out on the apparatus and its improvedresults will be discussed. The apparatus constituting the invention inits simplest form comprises a rotating centrifuge into which theberizable material, for example glass, is fed. The fiberizable materialis fed into the centrifuge from a glass tank forehearth or other sourcewhich heats it to a temperature Well above the lowest temperature atwhich it can be attenuated. The entry temperature Will, of course, vary,depending upon the constituents of the particular glass which isemployed but will be above the liquidus temperature thereof. Usingpresently available commercial glass, this entry temperature is fromabout r1800" F. to about 2000 F. The centrifuge has a drive mechanismfor rotating it at suflicient speed so that centrifugal forceimmediately causes the. glass to flow radially outward in the centrifugeand to .accumulate inan annular body on the inner Wall of the peripheryof the centrifuge.

In the apparatus embodying the invention the centrifuge has a `generallycylindrical periphery with a multiplicity of orifices drilledtherethrough, the orifices being arranged in, say, from one to ten ormore vertically spaced,rcir cumferential rows, and functioning to dividethe glass body and to form it into streams of molten glass, Ythe glassbeing forced through the orifices and projected outwardly therefrom asstreams by the centrifugal force created in the annular body of glass byrotation of the centrifuge. While it might be said that these glassstreams are projected radially outward from Vthe centrifuge, it will beappreciated, of course, that in plan view the streams 'do not extendradially but are swept backwardly due to the ever increasing radius ofeach outwardly thrown particle of glass without, of course,*compensatory increase in the angular velocity of these glass particles.As a result, and in common with all centrifuging operations, of course,the streams of glass sweep outwardly from the margin of the centrifugedbody in helices as can best be seen by Figure 7 of the drawings in thisapplication.

According to the invention the temperature of the glass is initiallyhigh enough so that the glass can be attenuated without the addition offurther heat thereto, and the apparatus of the invention does not havemeans for adding heat to the glass after it first enters the centrifuge.Instead, it is one of the improvements of the instant invention toprovide means for so controlling the environment into which the streamsare centrifugally projected from the centrifuge that heat willcontinueto be lost from the glass during its progression through the system butat a rate substantially lower than the rate of heat loss which wouldoccur if the environment were not controlled according to theinvention.k This control may be spoken of as retarding the rate Vof heatloss from the streams or as retarding the heat loss at a controlled rateby heating the gaseous environment in such a way as to maintain 'thetemperature of 4that environment at such level that Vheat is not addedto the glass during its passage through the environment and yet thatheat is not lost to the env-ironment from the glass at such a rate thatthe temperature of the glass streams will drop so rapidly as to fallbelow the attenuating temperature of the particular glass used prior tothe attenuation of the streams into fibers by the kinetic energy of theblast of gaseous medium.

The invention also includes the provision of means for the control ofambient gases. In common with all expanding jets of gaseous media, theannular blast of gaseous medium delivered from a blower arranged aroundthe centrifuge according vto the invention, has-a strong eductor effectand it induces a`large volume of gases into the system. These gases maybe ambient air, or other gases, and they may include the products ofcombustion-of heaters which are provided according to the invention forexercising control, not 'only over the rate of heat loss of the glassitself, but also'over the quantity or mass of the induced gases whichenter the system. The invention contemplates also the provision of meansfor controlling the actual mass of the gases induced by restricting thespace through which it is iiowed and thus quantity of gases introducedand, further, the provision of means for limiting the induction of theinduced gases to a certain location in the system whereby anydeleterious Yeifect of their induction is eliminated and the kineticenergy and/ or heat possessed by the induced gases contributes to theactual attenuating process.

The foregoing explanation is intended not only' as introductory to thefollowing specific description of apparatuses embodying the invention,but also to correlate terms to be employed in such description Vand inthe claims appended hereto as transferred from our earlier applicationand as first submitted herewith.

Figure l of the drawings is a diagrammatic showing of an apparatusembodying the invention `in its more elementary concepts as disclosedand claimed in our earlier application, which, in its commercial form,is better shown in Figures 3-7 of the drawings.

In Figure l, the elements of apparatus according to the inventioninclude a rotary centrifuge generally indicated at 20 which has an upperconical wall 21 leading to a vertical quill (not shown) which supportsthe centrifuge 20 and which is driven at high rotary speed, for example,by an electric motor. The centrifuge'20 may also include any one ofseveral types of glass distribution means so that a stream of glass feddownwardly through the quill and into the centrifuge 20 is distributedover the inner face of a peripheral wall 22 of the centrifuge 20. InFigure l, heavy glass streams are diagrammatically shown at 23 as beingthrown voutwardly from a glass distributor (not shown) and accumulatingin an annular body 2.4 against the inner surface ofthe wall 22 and areturn lip '25 of the centrifuge 20. Because of the rotation of thecentrifuge 20, the annular body 24 of glass is rotated and centrifugalforce causes the glass to flow through a plurality of stream-formingorifices 26 drilled in the generally cylindrical peripheral wall 22 ofthe centrifuge 2%. It will be appreciated, of course, that theparticular configuration of the separated glass streams 23, the body 24,and streams of glass 27 projected through the orices 26 are illustrativeonly and are not drawn with any attempt at a high degree of accuracy.

The streams 27 projected outwardly through the orifices 26 areattenuated somewhat in diameter although, of course, remaining highlyfluid according to the invention and the control inherent in thearrangement of structure and the cooperation between the structuralelements thereof as will be described below.

A first annular heater 28-is located above the peripheral portions ofthe centrifuge 20 which term includes both the peripheral wall 22 and laperipheral shoulder generally indicated at 29 on the conical return wall2l of the centrifuge 20. The annular heater-28 is illustrated in Figurel as being a gas burner and as having a plurality of concentric rows ofgas jet orifices 30 through which a combustible mixture of fuel, gas andair iiows from a manifold 3l which is fed from a supply line 32 undercontrol of a valve 33. As is roughly illustrated in Figure l, heat fromthe 'first annular heater 28 (indicated by the legend Flame Outline), isdirected downwardly on the peripheral shoulder 29 and the outer face ofthe peripheral wall 22 of the centrifuge 20* and to a first zonecircumjacent the centrifuge 20 through which the streams 27 areprojected by centrifugal force. While the ame outline from the iirstannular burner 28 is shown in Figure l as having a delinite'border, thisis, of course, not accurate and only generally indicates the zone towhich heat is applied from the first annular heater 28.

In the embodiment of Figure l, there is also a second annular heater 34.The second annular heater 34 is also a flame burner and is substantiallyidentical with the inner annular heater 28, although constructed -upon alarger radius and thus being radially spaced exteriorly of the firstannular heater 28. Like the iirst, or inner, annular heater 28, thesecond or outer heater 34 has a plurality of jet orifices 35 fed from acommon manifold 36 which is under the control of a separate valve 37 sothat each of the two heaters 28 and 34 may be independently controlled.This independent control of the two concentric and radially spacedannular heaters 28 and 34 constitutes an important facet of the instantinvention and makes possible control of the environment through whichthe streams 27 are projected, both in a first zone or environmentadjacent the centrifuge 20, and in a second zone or environment radiallyexteriorly of the first zone and comprising the zone of attenuationwherein the streams 27 are attenuated into iibers. As with respect tothe Flame Outline of the heater 28, the Flame Outline of the heater 34is also only illustrative- While heat from the two heaters 28 and 34 mayblend togetherV at the central portion of the annular space across whichthe streams 27 are projected, nevertheless each of the two concentricheaters 28 and 34 has independent control and the temperature conditionsin the two Zones or environments may be separately established andmaintained by this combination of apparatus.

lIn apparatus designed according to the invention the streams 27 are`attenuated by an annular blast, indicated bythe reference number 38`inrFigure l, which is'directed 427 are projected by centrifugal force.

.tioning of the second annular heater `gases is explained and includedas a part downwardly from an annular orifice 39 of a blower 40. Theblower 40 is concentric with and spaced radially from the centrifuge 20.The annular orifice 39 may continue unbroken around the entire blower 40or it may be formed by a plurality of separate minute orifices, whichmight be considered to be short slots. In either case, of course, theblast 38 is circumferentially continuous.

The blast is referred to herein as an attenuating blast or as anexpanding blast, the first relating to its function, and the second toone of its physical characteristics. In general the blast must havesucient kinetic energy so that it will be able to attenuate the glass.This is determined, of course, by the pressure maintained in the blower40 and by the area of the orifice 39 through which it is directed. Theattenuating blast must also be at a temperature which is controlled at alevel substantially above ambient temperature but substantially lowerthan the temperature maintained in the space between the centrifuge 20and blower 40. The temperature of the blast must not chill the system asa whole but it must be low enough so that the glass will rapidly coolafter it is attenuated into fibers.

Inherent in the operation of any such expanding jet as .a blast of steamor other gaseous medium emitted from a constricted orifice such as theorifice 39, there is an eductor effect which induces large volumes ofgases into the system. In fact, the instant invention includes withinits concepts, the provision of means for the deliberate induction ofgases and their utilization in the operation and in achieving the highlyrefined attenuation of long .fine 4fibers according to the invention. Inthe construc- `.tion illustrated in Figure 1, the eductor effect of theblast 38 induces ambient air over the top of the blower 40 through aspace which might be called an orifice, and which is generally indicatedby the reference number 41, .and into the annular space through whichthe streams The instant invention includes among its concepts means forthe control of its operation by control of the induced gases.

In the apparatus illustrated in Figure 1, these gases would be merelyinduced ambient air. The outer or second annular heater 34 is sopositioned relative to the blower 40 that it functions with the blower40 to define the induction orifice 41 and heat from the heater 34 isdirected across the path of the induced gases to raise their temperatureprior to their entry into the system. The effect of controlling both thequantity and the temperature of the induced gases by the apparatus ofthe invention will be more fully explained below with respect to theembodiment of the invention on a commercial scale, which apparatus isillustrated in Figures Although the legend Flame Outline is used inFigure l, the area delineated by each is not one in which .flame aloneis present nor one in which the -glass is .subject to heating .callycommented upon in our earlier application, and the .broken arrowsindicating the flow gases through the orifice 41 are not shown therein,the

of ambient induced eductor effect is inherent in any such blast and theposi- 34 in the position shown in Fig. l (Fig. 2 of our earlierapplication) establishes quantitative control over these induced gases.

In the instant specification, control over the induced of the improvedoperation resulting from the combination of the invenkor 39a.

ofthe streams as tion fromv two standpoints-(a) their temperature and(b) their quantity. Control of the temperature and/or quantity of theinduced gases results in control over the density of the induced gases,and since the kinetic energy of gases may be expressed as it can be seenthat the mass vof gas induced plays an important part in the process.Since the mass of induced gases depends upon their temperature andvolume, it follows that control of temperature and/ or quantity resultsin control of the kinetic energy and heat added to the system by theinduced gases according to the invention.

In Figure 2 of the drawings, there is shown a centrifuge 20a similar tothe centrifuge 20 shown in Figure 1, a first inner annular heater 28acorresponding to the first annular heater 28 in Fig. 1, a second annularheater 34a which'is radially spaced exteriorly of the first heater 28aand which corresponds to the second heater 34 of Fig. 1, and a blower40a corresponding to the blower 40 of Fig. l. In the modification of theinvention illustrated in Fig. 2, the first annular heater 28a is a gastired, radiant heater and has a domed ceramic 42 which is heated by aplurality of gas jets 30a spaced circumferentially around the heater 28aand which are fed with a combustible mixture from a supply line 32aunder the control of a valve 33a. 'I'he second annular heater 34a issimilar in all respects to the annular heater 34 of Fig. l andlike theheater 34 has a plurality of jets 35a fed from a common manifold 36aunder the control of an independent valve 37a. As in the apparatus shownin Fig. l, the centrifuge 20a of Fig. 2 has a peripheral wall 22athrough which there are drilled a plurality of stream forming orifices26a and the upper conical wall 21a has a peripheral shoulder portion29a. Glass which is flowed into the centrifuge 20a is distributed in hotstreams 23a over the interior of the peripheral wall 22a forming anannular body 24a thereagainst. Relatively heavy glass streams 27a areprojected outwardly through the stream forming orifices 26a across theannular space between the peripheral wall 22a of the centrifuge 20a anda blast 38a fed from an annular orifice 39a of a blower 40a.

Although the relative vertical levels of the centrifuge 20 and blower 40of Figure 1 differ from the relative vertical levels of the centrifuge20a and blower 40a of Figure 2, this difference is not intended as beingrestrictive of the invention. The vertical level between these twopieces of apparatus, each of which functions to carry out at least oneof the steps of the method embodying the invention, is critical only tothe extent that the blower 40 or 40a must be so positioned verticallyrelative to the centrifuge 20 or 20a that the streams 27 or 27a will beprojected outwardly and into the respective blast 38 or 38a at'a levelbelow the respective orifice 39 It is apparent, of course, that if therelative vertical levels of the centrifuges and blowers were such thatthe streams would be projected either against the blower housings orinto the blast at a point far removed from the -blast forming orice, theglass in the streams would, in the first instance, collect on thehousing, or, in the second instance, not be effectively attenuatedbecause the expansion of the blast would have reduced its kinetic energyto a point below that necessary for attenuation.

In the modification illustrated in Figure 2, as in that shown in Figurel, the two annular heaters 28a and 34a have independent controls; theinner heater 28a functioning to apply heat to the first zone of thegaseous environment through which the streams 27a are projected, andthus to reduce the rate of heat loss from those portions well as fromthe rotating annular body This irst annular body 'and portions of thestreams projected centrifugally from it. Again, as in the case of themodification shown in Fig. 1, the second annular heater 34a, which isradially spaced exteriorly of the rst heater 28a, functions to applyheat to the outer'part of the annular space through which the streams27a are projected for the purpose not only of controlling the rate ofheat loss from the streams therein, but of controlling the environmentin that second zone which includes the zone of the blast 38a. Inaddition, as in Figure 1, heat from the second annular heater 34a raisesthe temperature of gases which are induced over the corner of the blower40a and through the orifice generally indicated Vby the reference number41a, to approximately the level of the blast 38a.

The inner annular heater 28 or 28a of the modifications shown in bothFigures 1 and 2 is provided to the invention to control lthe temperaturenot only of yportions of the streams 27 and 27a, but of the rotatingannular bodies 24 and 24a of glass from which the streams are formed. Itwill be appreciated that in any such centrifuging structure, heatbrought into the system by the admitted molten glass is transferred byconduction, convection and radiation to all structural elements in thesystem and to the atmosphere surrounding the structure. A large quantityof heat is transferred directly to the body of the centrifuge 20 or 20aitself. Heat flows upwardly along the conical walls 21 and 21a of thesecentrifuges to the quills (not shown) on which they are mounted forrotation. The ow of heat upwardly along these conical walls 21 and'ZlaIis substantial because in any structure of this Itype it is necessaryto jacket the quills, for example, with cold water jackets, to preventdamage to the bearings upon which they are mounted and a substantialheat ow from the centrifuge results. If no heat control were exercisedin the system, great quantities of heat would be lost from the glass tothe centrifuge and eventually to the water jackets. Thus, the innerannular heaters 28 and 28a are provided according to the invention toreplace the heat lost from the glass to the centrifuge and the connectedapparatus, and thus to control the rate of heat loss from the glass inthe annular bodies 24 and 24a, reducing the heat loss from those bodiesto a rate substantially lower than that which -would prevail were it notfor the rst annular heaters 28 and 28a.

Simultaneously, the irst annular heaters 28 and 28a apply heat to theinner -part of the annular space between the centrifuges 20 or 20a andthe blasts 38 and 38a in the rst zone thereof so as to heat the firstenvironment into which streams are projected so that its temperature ismaintained at a level such that the rate of heat loss from the streamsis also retarded. The temperature level at which the yfirst environmentis maintained depends, of course, upon the entire operation but may bedefined as being below a temperature which would add heat, `i.e., raisethe temperature of the streams, and above a temperature at which heatlost from the streams to the environment would so 'cool the streams asto reduce their temperature to a level below the attenuating temperatureof the particular glass being iiberized before the streams areattenuated by the attenuating blasts 38 and 38a.

The second annular heaters 34 and 34a, which are 4radially spacedexteriorly of the first heaters are provided, according to theinvention, to control the rate of heat loss from the outermost portionsof the streamsby controlling the environmental temperature of the secondzone above described and they also act to control the induced gases, at#least in part. Were these gases to be 'induced at ambient temperature,they would rob heat from the system and from the streams, so reducingthe 'temperature ofthe streams as possibly to prevent their attenuationinto the very fine and long fibers which are produced-on apparatus ofthe invention. In addition, the exterior-annular heaters expand theinduced gases and thus.r-educetlieir masslper-unitof volume and-thusreduce ansiosa 8 the kinetic energy of these gases to a controlledlevel, so that they do not interfere with the clean entry ofthe streams27 and 27a into the expanding attenuating blasts 38 and 38a.

The control of the induced gases which is spoken jof hereinas eitherinvolving a reduction of their density, an increase of their temperatureor a reduction of their volume or mass, might Vlead to the suggestionthat lthe presence of induced gases is completely undesirable and',thus, to the suggestion that the induction of gases into the systemshould, if possible, be entirely prevented. This is not the case. Anyexpanding jet is accompanied byl an eductor effect which, if not atleast partially satistied, causes the jet or blast to plume or expandmuch more rapidly than would otherwise take place as the gases of thejet whinl and eddy upwardly to 'satisfy the vacuum created by theblast.It can be' seen in Figures l and 2 .that if the blasts were not suppliedwith at least a substantial proportion of the -gases required to satisfytheir eductor effects, the gases of the blasts 3S and 38u would eddyinwardly and upwardly, creating substantial turbulence and eddy currentswhich would have vseveral undesirable effects. First, since thedirection of movement of these eddy currents would be contra tothedirection of projection of the streams 27 and 27a, they would interferewith that projection. Secondly, the excessive `plurning 'or expansion ofthe blasts would reduce their kinetic energy available for attenuationmuch more -rapidly than if the blasts were kept relatively free of eddycurrents. Thirdly, it is of critical importance that the temperature ofthe glass streams upon penetration into the central high speed portionof the blasts 38 and v208i: shall be such that the blasts can attenuatethe streams effectively yinto fine fibers. If the streams are chilled totoo great a degree at the time of their entry into the attenuatingblasts, as, for example, by an excessive chilling effect of cold inducedgases or an excessive volume of induced gases, they are not attenuableto the degree possible if the temperature and mass of the induced lgasesare properly controlled.

The discussion of I he effects of these various facets of 'a processcarried out by operation of apparatus designed according to theinvention is based upon the observation of experimental operation ofsuchapparatuses wherein the various conditions are changed under control.Most eifective production of fine glass fibers is accomplished when theapparatus is all operated to carry out all of the teachings of theinvention. When only some of these teachings are put into effect, theresults still represent substantial improvements in the degree ofattenuation Vachieved and in the qual-ity of the fibers producedby priorart methods and apparatuses. Each additional con- -cept underlyinginvention which is added results in a further improvement. As anillustration, an apparatus substantially identical in its major partswith the apparatuses illustrated in Figures 1,1 and 2, but notincorporating any means for the control of ambient induced gases, may beable to attenuate fibers to average diameters in the order of, say,.00025 inch from streams of certain diameter and temperature projectedat certain speeds. lf means are then added for controlling and `reducingthe quantity of the induced gases so that the mass of the gas, and thusits kinetic energy is reduced, the liber diameters will drop, say, to.00021 inch. If the second, outermost annular heater is then utilized toraise the temperature of the induced gases to, say, approximately thetemperature of the attenuating blast, the diameter of the producediibers will dropy to as low -as,-'say, .000116 to .00018 inch.

The desirability of these finer fibers becomes immediately apparent whenthe resulting insulating capability of a mass of the fibers produced isdetermined. In general, it may be said that for any given thickness andapparent density of glass liber insulating mat, theinsulatingqualityincreases asthe Iaverage diameter r`of the fiber vtheheavy stream of glass 53 making up the mat decreases. It is thusdesirable in commercial production to fabricate bers as line as possibleand as nearly uniformly as possible, which objects are apparatusembodying the make the final product difficult to handle in use. In

sharp contrast, masses of fine long bers produced on the apparatus ofthe invention form insulating mats of considerable strength, capable ofwithstanding rough handling in their commercial uses. Parting strengthis an expression of the force in pounds per unit of weight required topull a sample apart. It is measured by tting a doughnut shaped sectionof the material over two rods and pulling the rods apart until thesample separates into two pieces. For any particular apparent densityand thickness of sample, the higher parting strength is indicative oflonger, stronger and more nearly uniform fibers.

Apparatus embodying the invention and suitable for the commercial use isdisclosed in Figures 3-7. This apparatus embodies the inventionoriginally disclosed and claimed in our earlier application identifiedabove and as modified and improved according to the teachings of theinstant application for the achievement of practical commercialproduction. ln the portion of this specification which follows,therefore, this apparatus will be described in detail and correlationbetween the apparatus set forth and the basic concepts inherent in ourearlier application and described above, will be made.

Figure 3 shows a multiple unit, commercial set up,

embodying the instant invention in all of its refinements. A glass tank50 is fragmentarily shown as leading to an elongated forehearth 5l.Molten glass suitable for attenuation into ne fibers is fed from thetank 50` and along the forehearth 5l above its liquidus temperature.Spaced along the forehearth 51 are four stream-forming bushings 52 eachof which controls the discharge of a heavy stream of molten glass 53into a iiberizing unit 54 embodying the invention. Each of theiiberizing units 5'4 is mounted by rollers 55 on a pair of transverserails 56 which are supported by heavy cross beams 57. Each of the units54 may be moved laterally away from the production line to the positionindicated by the broken lines 54a (Fig. 4) when necessary for repair ormodification. Each of the production units 54 comprises a drive unit 50which rotatably supports and drives a quill 59 (Fig. 5). The quill 59 ismounted for rotation by an upper bearing 60 and a lower bearing 61 andis tubular in shape, providing a vertical central opening 62 through`which flows downwardly. The drive unit 58 has a cooling jacket 63 andis carried by heavy cross brackets 64 on which the rollers 55 aremounted.

The lower portion of the quill 59 extends downwardly through an annularheater unit generally indicated at 65 and comprising two concentric,annular manifold chambers, an inner chamber 66 for an inner heater 67,and an outer manifold 68 for an outer heater 69 which is radially spacedexteriorly of the first annular heater 67. The unit 65 is supported fromthe bottom of the drive unit 58 by a heavy tubular flange 70 and, inturn, adjustably supports a tubular water jacket 71. 'Ihe water jacket71 has a downwardly extending tubular portion 72 circumjacent aconsiderable length of the quill 59 and a horizontal flanged portion 73extending outwardly across the space between the top of the burner unit65 and the bottom of the drive unit 58.. Coolant for the jacket thedrive unit jacket 63: is carried to and from the unit 54 by pipes 74located at the upper part of the drive unit 58. y

A rotary fiber forming centrifuge generally indicated at 75 is removablysupported at the bottom of the quill 59 and an annular gaseous blowergenerally indicated at 76 is suspended lfrom the heater unit 65 atthemlevel of the centrifuge 75. The centrifuge 75 and the blower 76ybound an annular space, generally indicated at 77, across which streamsof `glass 78 are projected from Ithe centrifuge 75. The blower 76 has aplurality of orifices 80 which extend circumferentially around its innerwall and through which a heated gaseous medium under pressure, such assteam, is fed from its interior manifold 79. The gaseous medium forms adownwardly moving, annular at-tenuating blast having high kineticenergy. The centrifuge 75 is rotated a-t such speed that the streams 78are projected therefrom with sufficient force to penetrate the turbulentinner margin of the blast Vand into its high velocity central por-tionwhere the molten glass in the streams '78 is subjected to the force ofthe blast and attenuated into .a plurality of very fine fibers of greatlength, the veil of fibers thus formed being generally indicated at $1.A heavy guard 82 surrounds the attenuating area, the guard 82 beingremovablysupported by suitable brackets from the lower side of theburner unit 65.

Hanger straps 83 depend from the cross beams 57 and support a binder gununit 84 beneath the centrifuging unit. The binder gun unit 84 comprisesa guide 85 and a plurality of downwardly and inwardly directed binderspray guns 86 which are fed with air and suitable binder from supplypipes S7 and 88. The binder guns 86 are circumferentially spaced bybrackets 89 around a ring 90 and are tiltable in the brackets 89 so thatsprays of binder material may be directed inwardly onto the tubular veilof fine fibers 8l moving downwardly through the binder gun guide 85. v Ahood generally indicated at 91 in Figures 3 and 4 is spaced below theunits 54 and has an open upper end for the entry of the several veils ofdownwardly moving fibers 81 and a lower open end which closely overlies'an accumulating conveyor 92. The veils 81 are lapped back and forth inthe hood 91 for accumulation on the conveyor 92 by the action of a pairof alternately energized air jets 9G (Fig. 4) located at opposite sidesof the hood 91, there being a pair of jets 93 for each of the units 54and thus each of the veils 8.1. By transversely lapping the veil offibers S1, they are built up in ever thickening layers upon theforwardly moving conveyor 92. The large volume of gases carrieddownwardly into the hood 91 is exhausted through a chamber 94 whichextends beneath the conveyor 92 and is connected by a suitable duct 95to exhaust blowers (not shown). The conveyor 92 preferably is fabricatedfrom link chain or similar material so that the gases will readily passthrough the conveyor 92 into the exhaust chamber 94. The conveyor `92 ismounted upon and driven by a plu rality of conveyor rollers 96 andclosely abuts the receiving end of a furnace conveyor 97 (Fig. 3). Anaccumulated blanket 98 of fibers is carried out of the hood 91 by thereceiving conveyor 92 and compacted somewhat by a pressure roller 99 atthe outlet side of .the hood 91. The blanket 98 is carried by thefurnace conveyor 97 through a furnace 100 in which the binder applied tothe veils of rlibers 81 from the binder gun The portions of thecommercial apparatus illustrated in Figs. 3-7 which correspond to theapparatuses shown in Figs. l and 2 are shown in detail in Figs. 6 and 7.The centrifuge 75 has a peripheral wall 110 which is illustrated in Fig.6 as being slightly conical in shape but be formed as a cylinder orconed in in the terminology generally cylindricalf. The peripheral wall110 is integral with and supported bya. conical, Ianged, top wall i111and has an inwardly directed, L'conical return lip 112. At the upper,inner edge of the 'conical Wall 111 the centrifuge 75 has a turned overannular lip 113 by which it is supported on an outwardly directed flange1114 at the bottom of the quill 59. The centrifuge 75 is mounted on thequill 59 by laplurality of Imounting bolts 115 which extend through a`mounting `ring 116, the ange 113 of the centrifuge 75 and the iange 114of the quill 59. The ybolts 1.15 also extend 'through an outwardlydirected flange 117 which supports 'a cup-shaped distributor generallyindicated at 118.

The distributor 118 is illustrated in the drawings as ihaving animperforate bottom 119 and an outwardly flared, circular side wall 120.The molten glass 'stream 53 drops downwardly by gravity through thehollow `-quill 59 and against the bottom 119 of the distributor I118.Since the distributor l118 is mounted on the quill S9-with thecentrifuge 75, centrifugal force causes the glass from the stream 53to'ilow radially outward across the bottom 119 (see also Fig. 7) andagainstrthe inner "surface of the wall 126. A .relatively thick layer ofglass indicated at 121 forms on the inner surface ofthe Wall 120. The-wall 120 is perforated with a substantial vnumber of large diameterorifices 122 through which gglass from the layer 121 is centrifugallythrown as heavy distribution streams 123.

Glass in the distribution streams 123 impinges against the inner surfaceof the peripheral Wall 111i` of the centrifuge 75 and re-combines toform an annular body of glass generally indicated at 124. The peripheralwall l110 of the centrifuge 75 is perforated by a very large num- -berof minute orifices 125 through which centrifugal A'force flows glassfrom the body 124 and from which streams 78 of the molten glass areprojected outwardly lacross the annular space generally indicated at 77.The outwardly projected streams of molten glass 73 are projected withsuch force as -to enter but not go through, i.e., to penetrate throughthe turbulent margin and enter into the interior high velocity portionof the blast of gaseous medium delivered downwardly from the `annularorifices 8() of the blower 76. In the commercial'embodiment of apparatusfor carrying out the process of the invention as practiced in thestructure illustrated in Figs. `3-7, the blower 76 employs steam underpressure. The Llrinetic energy of the steam attenuates the heavy streams78 into ne, long fibers directing them downwardly in the 'hollow veilS1.

The quill S9 has an internal water jacket 126 which l'cooperates withthe tubular portion 72, of the jacket :7.1 in order to prevent the ow ofheat from the centrifuge 'ange 113 upwardly along the quill 59 whichwould, of course, damage the bearings -61 and 62 and the motor of thedrive unit 58. In addition, interiorly ofthe quill '59, there is a smallburner 127 having -a few ilame orifices .128 that are directeddownwardly into the-interior of the distributor 118. The burner 127 isnot tired during the normal operation of the apparatus of the Vinventionbut is employed at the time of initial start-up in order to prefheat thedistributor 118 so that it will not excessively chil-l -the molteniglass in the stream 53 when it is tirstadmitted thereto. IBecause heglass in the stream 53 is at'its highest temperature when it lirstenters the apparatus, the distributor 113 quickly reaches a high enoughtemperature fand is thereafter kept hot by new glass so that theinternal burner 127 is no longer necessary. tIt is, therefore, turnedolf a few minutes after the operation is initiated.

Apparatus designed according to the invention controls the temperatureof the glass in the body 124 and in the vstreams 78 as they areprojected across the annular space 77 by means of the inner annularheater 67 and outer an- -ular heater 69, as discussed above inconnection with JFigs. 1 and 2. The inner burner 67 is fed with a com-:bustible mixture of gas and air from its mariifold66. Theburner 67 hasa stepped oriiice plate 129-whichis 12 fabricated from refractorymaterial and is mounted at the bottom kof the manifold 66 by retainingrings 130 and 131. The lorifice plate 129 has several concentric,circular rows of'oriftces indicated as a group by the refer- ,encenumber 132 all of which are formed in a horizontal portionof the orificeplate 129 and all of which are positioned vertically above a shoulderportion 133 of the -centrifuge 75, indicated by the bracket in Fig. 6.The orifice plate 129 and the several rows of orices 132 are ,spacedabove-the shoulder portion 133 of the centrifuge 75 a distancesuch thatthe hottest parts of the liames Aburning from the orices 132 are locatedat or very close to the surface of the shoulder portion 133.

The orifice plate `129 in the apparatus shown in the `drawings also hasseveral, downwardly stepped, concentric, circular rows of oriiices 134,135, 136 and 137. 'Eachof the rows 1344137, inclusive, is steppeddownwardly such a distance from its predecessor that the total of all ofthe distances'is approximately equal to the vertical dimension of theperipheral face of the centrifuge 75. The'flames burning 'from theorices in each of the successive rows 134-137, therefore, have theirhottest parts-staggered or stepped'downwardly adjacent the face 11G toachieve'nearly uniform heat application over the entire face 110.

The heating zone of the inner heater 129 is defined and heat `from itsflames directed into the lirst zone of the annular space 77 Aby a pairof air direction rings 13S and 139. The inner air direction ring 138functions to greatly restrict the ow of induced gases downwardly aroundthe quill 59 or between the quill 59 and the water jacket 72, or innerwall of the manifold 66, so as to reduce as much as possible any effectthat gases entering the system from this point would have upon thetemperature and forces present in the annular space 77, and to preventthe flow of hot combustion igases from heater `129 upwardly around thequill 59.

The outer air direction ring 139 is a part of the apparatus provided forinduced gas control according to the invention. The attenuation guard 82is supported `from the burner unit 65 by a support ring 140 removablyheld in place on an annular flange 141 by removable pins 142. The flange`141 depends rom several mounting bars 143 which `are secured to theburner housing 65. (See also Fig. 5). vAn open space indicated by thebroken arrows in Figure 6 is thus provided through which ambient air isdirected into the space above the blower 76 and below the burner unit65. An air limiting ring 144 extends part way acrossthis space to limitthe ow of -gases therethrough and an induced air orifice 145 is formedby the inner upper corner of the blower 76 and the outer side of the aircontrol ring 139. The second, or outer, annular heater 69 has an orificeplate 146 in which there are formed several rows of orifices 147. Acombustible mixture of gases from the manifold 68 of the heater 69 isfed through the orifices 147 at such rate as to heat air induced intothe space above the blower 76 to a temperature approximating thetemperature of the lattenuating blast emitted from the orifices 8) ofthe blower 76. The combustion gases from the outer heater 69 are inducedto flow with the ambient induced air through the air control orifice 145and downwardly into the annular space 77 where their heat and kineticenergy cooperate with the attenuating blast to control thetemperatureand attenuation of fibers from the streams 78.

We claim:

1. Apparatus for the attenuation of ne fibers from heat softenablevitreous material, said apparatus comprising a metallic centrifuge andmeans for rotating the same, means for supplying owable softenedmaterial to said centrifuge, said centrifuge having a plurality ofstream forming orifices in its periphery, a first annular heat-sourcelocated externally of and near the periphery ofV said centrifuge forapplying heat to a zone including the periphery of said centrifugeforretarding heat loss from the material therein and from materialissuing from the orices as streams and to at least a part of saidstreams, means for controlling said annular heat source, a secondannular heat source located radially exteriorly of the rst said heatsource and spaced radially therefrom for applying heat to a second zoneradially exterior of said rst zone and including at least a part of thelength of said streams where the diameters are being reduced byattenuation to bers for retarding the rate of heat loss therefrom, meansfor controlling said second heat source independently of said first heatsource and an independently controlled annular blower located radiallyexteriorly of said rst heat source for applying tractive forces to bersattenuated from said streams, one of said heat sources and said blowerdening therebetween an annular passageway open outwardly to thesurrounding atmosphere for the flow of gases induced therethrough bysaid blower.

2. Apparatus according to claim l in which the rst heat source is aburner having a flame playing in the rst zone.

3. Apparatus according to claim 2 in which at least one of said heatsources is a source of radiant energy.

4. Apparatus for the attenuation of ne bers from streams of hot glassprojected outwardly by a centrifuge, said apparatus comprising, incombination, a rst annular heat source concentric with, external of andlocated near the periphery of said centrifuge for applying heat to azone including the periphery of said centrifuge for retarding the rateof heat loss from said vglass streams issuing therefrom as streams andto at least the rst part of said streams, means for controlling saidannular heat source;

Van independently controlled annular blower concentric with and spacedexteriorly of said heat source for directing a high velocity blast ofgaseous medium to apply tractive forces to bers attenuated from saidstreams, a second annular heat source spaced radially outwardly from therst said source for applying heat to a zone radially exterior of the rstsaid zone and that includes at least part of the zone of said blast ofgaseous medium for retarding the rate of heat loss from said glassstreams therein and means for controlling said second heat sourceindependently of said rst heat source, one of said heat sources and saidblower dening therebetween an annular passageway open outwardly to thesurrounding atmosphere for the ow of gases induced therethrough by saidblower.

5. Apparatus for attenuating ne bers from berizable material, saidapparatus comprising, in combination, a rotary centrifuge the peripherytheroef having a plurality of stream forming orices therein, annularheat source positioned for applying heat onto the periphery of saidcentrifuge and into a rst zone adjacent the periphery of saidcentrifuge, an annular blower having its blast emitting orice radiallyspaced from said heat source and `directed axially of said centrifuge,said heat source and said blower dening therebetween an annularpassageway open outwardly to the surrounding atmosphere, said bloweracting to apply tractive forces to bers attenuated from said streams andto induce gases through said passageway into the space between theperiphery of said centrifuge and said blower.

6. Apparatus for attenuating ne bers from berizable material, saidapparatus comprising, in combination, a rotary centrifuge the peripherythereof having a plurality of stream forming orices therein, a rstannular heat source positioned for applying heat onto the periphery ofsaid centrifuge and into a rst zone adjacent the periphery of saidcentrifuge, an annular blower having its blast emitting orice radiallyspaced from said heat source and directed axially of said centrifuge,said heat source and said blower dening therebetween an annularpassageway open outwardly to the surrounding atmosphere, said bloweracting to apply tractive forces to bers attenuated from said streams andto induce air through said passageway into the space between theperiphery of said centrifuge and said blower, and a second annular heatsource radially spaced exteriorly of the rst said heat source andpositioned for heating the induced air prior to its entry into suchspace and thereby to reduce the density of such induced air.

7. Apparatus for atenuating ne bers from berzable material, saidapparatus comprising, in combination, a rotary centrifuge the peripherythereof having a plurality of stream forming orices therein, an annularheat source positioned for applying heat onto the periphery of saidcentrifuge and into a rst zone adjacent the periphery of saidcentrifuge, an annular blower having its blast emitting orice radiallyspaced from said heat source and directed axially of said centrifuge,said heat source and said blower dening therebetween an annularpassageway open outwardly to the surrounding atmosphere, said bloweracting to apply tractive forces to bers attenuated from said streams andto induce air through said passage- Way into the space between theperiphery of said centrifuge and said blower, and control means forlimiting the mass of air induced through said passageway for onlypartially satisfying the eductor requirements of said high velocityblast.

8. Apparatus for the continuous attenuation of ne bers from heatsoftened glass comprising, in combination, a rotary centrifuge having amultiplicity of stream forming orifices in its periphery, means forsupplying molten glass at attenuating temperature to said centrifuge,means for mounting and rotating said centrifuge on a vertical axis atsuch speed as to centrifugally project streams of molten glass outwardlythrough said orices, an annular steam blower housing concentric with andradially spaced exteriorly of said centrifuge and dening with saidcentrifuge an annular space through which said streams are projectedfrom said centrifuge, said blower having a blast orifice located abovethe level of projection of said streams and `directed doumwardly at theouter side of such space, the blast from said steam blower acting toapply tractive forces to bers attenuated from said streams and to inducegases into such annular space by its eductor effect, an annular heatermounted concentrically with said centrifuge for applying heat to theperipheral portions of said centrifuge and to a zone circumjacent saidcentrifuge and comprising principally the inner part of such space, saidblower and said heater dening therebetween an annular passageway openoutwardly to the surrounding atmosphere for ow of such induced gasesinto such annular space, and annular means concentric with and radiallyspaced exteriorly of said centrifuge and said annular heater forcontrolling the density of such induced gases.

9. Apparatus for the continuous attenuation of ne bers from heatsoftened glass comprising, in combination, a rotary centrifuge having amultiplicity of stream forming orices in its periphery, means forsupplying molten glass at attenuating temperature to said centrifuge,means for mounting and rotating said centrifuge on a vertical axis atsuch speed as to centrifugally project streams of molten glass outwardlythrough said orices, an annular steam blower having a downwardlydirected blast concentric with and radially spaced exteriorly of saidcentrifuge, said blast dening with said centrifugev an annular spacethrough which said streams are projected from said centrifuge, the blastfrom said steam blower acting to apply ltractive forces to bersattenuated from said streams and to induce gases into such annular spaceby its eductor eect, an annular heater mounted concentrically with saidcentrifuge for applying heat to the peripheral portions of saidcentrifuge and to a zone comprising principally the inner part of suchspace, said steam blower and said heater dening therebetween an annularpassageway open outwardly to the surrounding atmosphere for flow of suchinduced gases into such annular space, and a second annular heaterconcentric with amorosa :zand radially spaced eXteriorly of the rst saidannular heater for heating such induced gasesprior to entry into fuge,said blast defining with said centrifuge an `annular space through whichsaid streams are projected from said centrifuge, an annular heatermounted concentrically with said centrifuge and radially spaced`interiorly of said steam blower for applying heat to the peripheralportions of said centrifuge and to a zone comprising principally theinner part of such space, the blast from said steam blower acting toapply tractive forces to fibers attenuated from said streams and toinduce ambient gases into such annular space by its eductor effect,means mounted concentrically with said centrifuge andat the.

inner side of said annular heater for severely restricting `the flow ofambient gases between said centrifuge and said annular heater into suchannular space, and annular control means concentric with andv radiallyspaced eX- teriorly of said centrifuge and said annular heater forcontrolling the flow of induced gases through the space between saidannular heater and said steam blower.

1l. Apparatus for the continuous attenuation of fine fibers from heatsoftened glass comprising, in combination, a rotary centrifuge having amultiplicity of stream forming orifices in its periphery, means forsupplying molten glass at attenuating temperature to said centrifuge,

kmeans for mounting and rotating said centrifuge on a vertical axis atsuch speed as to centrifugally `project streams of molten glassoutwardlythrough said orifices, an annular steam blower housingconcentric with and radially spaced exteriorly of said centrifuge andden- `ing with said centrifuge an annular space through which saidstreams are projected from said centrifuge, said `blower having a blastorifice located above the level of projection of said streams anddirected downwardly at the outer side of such space along the inner faceof said steam blower housing for attenuating said streams into finefibers, means for substantially preventing the fiow of ambient gasesthrough the inner par-t of such Space, the

'blast from said steam blower acting to induce ambient gases through theouter partof such annular space by its 'eductor effect, an annularheater mounted concentrically with said centrifuge for applying heat tothe peripheral portions of said centrifuge and to a zone comprisingprincipally the inner part of such space, said steam blower and saidheater defining therebetween an annular passageway open outwardly to thesurrounding atmosphere for flow of such induced gases into such annularspace, and a second annular heater concentric with and radially spacedexteriorly of said centrifuge and of the first said annular heater forheating such induced gases prior to entry into such annular space.

12. Apparatus according to claim 11 in which the first annular heater ispositioned in part above the peripheral portion of the centrifuge andabove the inner fpart `of the annular space, the annular vsteam blowerthousing cooperates with the housing of one of said annular heaters toform an annular orifice for saldV induced gases leading into suchannular spaceand the second said annular heater is located for directingits heat across such annular orifice for preheating such induced gasesto reduce the density thereof.

13. Apparatus for the continuous attenuation of fine fibers from heatsoftened glass comprising, in combination, a rotary centrifuge having amultiplicity of stream forming orifices in its periphery, means forsupplying molten glass Vat attenuating temperature to said centrifuge4-and means for mounting and rotating said centrifuge on a vertical axisat such speed as to centrifugally project streams of molten glassoutwardly through said orifices, an annular steam blower concentric withand radially `spaced eXteriorly of said centrifuge defining with saidcentrifuge an annular space through which said streams VLare projectedfrom said centrifuge, an annular heater mounted concentrically with saidcentrifuge and radially interiorly of said blower for applying heat tothe peripheral portions of said centrifuge and to a zone comprisingprincipally the inner part of such space, said steam blower and saidannular heater defining therebetween an annular passageway openoutwardly to the surrounding atmosphere for flow of reduced gases intosuch annular space, said blower having a blast orifice located above thelevel of projection of said streams and directed Adownwardly at theouterside of such space for attenuating said streams into fine fibers,the blast from said steam blower acting to induce ambient gases intosuch annular space by its eductor effect, and means for substantiallypreventing the flow of ambient gases through the space 'between saidcentrifuge and the inner side of said'annular heater.

14. Apparatus according to claim 13 and a second Aannular heaterconcentric with and radially spaced ex- `teriorly of the first saidannular heater for preheating such induced gases prior to their entryinto the annular space to reduce the density thereof.

15. Apparatus according to claim 13 in which the face of the peripheryof the centrifuge is generally cylindrical and in which the annularheater is a gas burner having a plurality of concentric circular rows ofjet orifices leading from a common manifold, there being at least onerow of orifices overlying the peripheral portions of the centrifuge andmore than one row of orifices stepped down vertically and extendingalong radii progressively 50 greater than the radius of the periphery ofsaid centrifuge,

`each other distances totalling approximately the vertical the steppeddown orifices being spaced vertically from dimension of the face of theperiphery of said centrifuge whereby said face of said centrifuge isevenly heated.

References Cited in the file of this patent UNITED STATES PATENTS v2,328,714 Drill et al. Sept. 7, 1943 2,497,369 Peyches Feb. 14, 19502,525,970 Spier et al. Oct. 17, 1950 2,587,710 Downey Mar. 4, 19522,609,566 Slayter et al Sept. 9, 1952 2,624,912 Heymes et al. Jan. 13,1953 2,707,847 Anliker May 10, 1955 2,816,826 Brennan Dec. 17, 19572,881,471 Snow et al. Apr. 14, 1959

